Proponents of a tax measure rivaling Gov. Jerry Brown's Proposition 30 threw the first punch in the competition Tuesday, issuing an ad criticizing the governor's tax as a windfall for Sacramento politicians and pulling Brown into a battle he had hoped to avoid.

The 30-second ad began airing statewide Tuesday saying, "Don't be misled by the politicians. To really help our schools, vote yes on 38." The ad shows money flowing into a schoolhouse but then flowing out into the hands of politicians while a youthful-sounding narrator says, "That's why Sacramento's behind it."

The move was notable not only because Brown had worked to avoid well-funded attacks on his proposed tax, but also because Prop. 30 proponents pleaded Monday with the principal backer of Proposition 38, wealthy Southern California civil rights attorney Molly Munger, not to air the attack ad.

Another group opposed to Prop. 30, which has received tens of millions of dollars from Charles Munger Jr., Molly Munger's brother, was already airing ads against the initiative.

Brown's campaign team fired back, calling the Mungers the children of a billionaire whose legacy could be that of eviscerating funding for public schools. They derisively labeled the action as the "Munger Games," a play on the title of the novel and film "The Hunger Games," about a future in which children are forced to compete in a battle to the death.

Dan Newman, spokesman for Prop. 30, said, "It's hard to imagine how attacking Prop. 30 could help her initiative. It really makes you question her true motivation here."

Munger's campaign said it had launched the ad as a response to pro-Prop. 30 ads saying money raised by Brown's measure would go to schools and "can't be touched by Sacramento politicians."

In fact, Prop. 30 would free up billions of dollars that would be spent by the Legislature and the governor.

The campaigns for both measures argue theirs is the best solution to increasing public school funding in California.

Brown had sought to avoid a highly visible negative campaign against Prop. 30. He either won support from, or neutralized, most business organizations in the state that typically fund campaigns against tax increases.

Various polls show that Prop. 30 has a slim lead among voters while Prop. 38 is far short of the majority needed for passage. If both were to win, the one that receives the most votes would take effect.

Then came Molly Munger and her brother, who has given about $23 million to a committee that is working against the governor's tax measure.

"It's hard enough to anticipate one well-financed opponent showing up in the 11th hour. It's even harder to imagine two well-financed opponents showing up ... and it's absolutely impossible to have imagined that the two of them would be brother and sister," Schnur said. "You don't learn this one in campaign-strategy school."

Sherry Bebitch Jeffe, a policy and politics fellow at the University of Southern California and a veteran analyst of California politics, said she doesn't question the Mungers' motivations.

"These are not elected officials. They're not venture capitalists buying up and closing down corporations," Bebitch Jeffe said. "They're using their money to, at least in their minds and in the minds of some voters, better society and better education."

Prop. 30 would increase the sales tax by one penny for every four dollars spent for four years and would increase the income tax on the state's highest earners for seven years, generating about $6 billion per year.

The additional tax revenue would lead to an increase for schools via the voter-mandated education funding formula of Proposition 98, and it would also generate money for other state services. If it fails, the budget contains nearly $6 billion in automatic spending cuts that would fall almost entirely on public schools, colleges and universities.

Former President Bill Clinton endorsed the measure at a rally for congressional candidates at UC Davis on Tuesday.

Prop. 38 would increase the personal-income-tax rate on nearly all Californians for 12 years, generating about $10 billion per year. Most of the money would have to be spent on public schools, though some would go to paying the state's debt.